Oscillating power tools employ side to side vibratory motion to cut or work upon materials. A rear mount of the blade removably attaches to a head of the power tool. A working front element of the blade is further attached to the rear mount portion, typically permanently. In one common configuration, the working end is of sheet metal or similar flat form including a toothed front end. This blade moves against a work piece to cut into the piece. Such blade most often is of elongated rectangular shape with straight edged sides and teeth distally positioned along the front edge. The rectangular blade shape is useful for its ability to make controlled slot sizes and locations, while other shapes such as round with peripheral teeth are known and commonly used for side cuts and drywall for example. Other shapes include tapered with a wider front end and narrower portion to the rear. These blades can provide blind plunge cuts where a cut is closed at both sides. However, they provide limited control in holding a side position whereby the width of a cut can be hard to control.
The rectangular configuration is particularly popular among the available blade styles. It works adequately for cutting narrow items such as loose wood moldings or metal bars. In this case the blade is wider than the object to be cut and the slot that results is exposed on both sides. In this manner the saw dust or equivalent debris can readily be ejected sideways out from the cut. Similarly a cut may be done at one edge of the work piece; the debris then ejects out of the one exposed side for reduced but still usable results. However when this type of blade is used for a blind plunge cut, with the cut slot closed at both ends, there is no practical exit opening, channel, or action for the debris.
The blind plunge cut is especially common in wood. As the wood work piece becomes thicker the effect of the blocked exit channel becomes more pronounced. For example, common wood cutting blades are rated for up to a 2 inch nominal wood thickness, or about 1.5 actual inches deep. In fact such cuts with prior rectangular blades are not practical without undo effort and stress upon the tool and user. Therefore a conventional rectangular blade can cut a central area of a thick work piece only by plunging progressively across the width of the work piece from an edge.
A further limitation of the rectangular blade is its inability to cut directly sideways from an initially cut slot. To create a wider slot, for example to fit an electrical switch box in a wood or other panel, a further plunge cut is required adjacent to a prior one. This is not convenient and is hard to control the slot position and size.